Keys to Initiating Clinical Care
in Radiological Emergencies
Robert Emery, DrPH, CHP, CIH, CSP, RBP, CHMM, CPP, ARM
Assistant Vice President for Safety, Health, Environment & Risk Management
The University of Texas Health Science Center at Houston
Associate Professor of Occupational Health
The University of Texas School of Public Health
Center for Biosecurity and Public Health Preparedness
www.texasbiosecurity.org
Abstract
Keys to Initiating Clinical Care in Radiological Emergencies
When compared to other emergency situations, radiation overexposure events are
relatively rare events, so many clinicians may not be experienced in the treatment
these victims. Regardless of whether a radiological event was intentional (e.g.
terrorism) or accidental, appropriate medical care is generally predicated by the
dose delivered. But the clinician may not be equipped to estimate this dose.
Conversely, a health physicist (radiation safety professional) can help with
estimating the dose, but may not be knowledgeable of the appropriate medical
interventions. To address this predicament, this presentation will:
Describe the main types of overexposure events
Identify the information needed to estimate the radiation dose received
Provide examples of dose reconstruction calculations for the main types of
overexposure scenarios
Describe how this information impacts the medical tests and procedures to
be applied
Review the regulatory reporting requirements in cases of radiation
overexposure
Discuss the emerging issue of possible acts of domestic nuclear terrorism
Provide a list of useful web and text references
Learning Objectives
Describe the main types of overexposure events based on a 45 yr
review of case reports in Texas
Review the regulatory reporting requirements in cases of
radiation overexposure
Identify the information needed to estimate the radiation dose
received
Provide examples of dose reconstruction calculations for the main
types of overexposure scenarios
Describe how this information impacts the medical tests and
procedures to be applied
Identify resources for further assistance
Discuss the emerging issue of possible acts of domestic nuclear
terrorism
Provide a list of useful web and text references
Radiation Uses
Sources of radiation are used to society’s
benefit in a number of industries
„
Manufacturing, construction, medicine, safety
Like combustion, electricity, and high
pressures, when used appropriately, can be
very safe, but if misused, can result in harm
Possible Radiation Effects
Acute (immediate) and chronic (long term)
effects
Acute effects
„
<100 rem
Š no immediate effects
„
100-200 rem
Š Mild nausea, vomiting
Š Loss of appetite
Š Malaise, fatigue
„
200-400 rem
Š
Š
Š
Š
Nausea universal
Hair loss
Diarrhea, fatigue
Hemorrhages in mouth, subcutaneous tissues, kidneys
Radiation Effects
Acute effects (con’t)
„
400-600 rem
Š Mortality probability 50%
„
600-1,000 rem
Š
Š
Š
Š
„
Bone marrow destroyed
GI tract affected
Internal bleeding
Survival dependant upon prompt medical intervention
>1,000 rem
Š Rapid cell death
Š Internal bleeding, fluid loss
Š Death likely within hours
Radiation Effects
Chronic effects
„
„
„
„
Possible effects on immune system
Possible increased risk of cancer (estimates vary
with rate of delivery of dose. For acutely
delivered doses, 1 x 10-3 increased cancer
fatalities per rem)
Possible damage to reproductive systems can
result in mutations passed on to subsequent
generations
Psychological effects
The Basic Problem
In cases of radiation exposure events, the
recurrent question will always be: what is the
dose?
„
„
A health physicist can help with estimating
the dose – but do they have an
understanding of the medical procedures
to be dictated?
A physician can provide medical care – but
do they have an understanding of radiation
exposure issues?
Annual Radiation Dose Limit Primer
Occupationally exposed individuals
„
„
„
5 rem to the whole body
50 rem to skin and extremities
15 rem lens of eye
Occupationally exposed minors
„
0.5 rem
Occupationally exposed embryo/fetus
„
0.5 rem for the gestation period
General public 0.1 rem
Note: limits for total dose from sources
external and internal to body
Overexposure Reporting Requirements
Area
24 hour
affected
notification
Whole body >5 rem
Immediate
notification
>25 rem
Lens of eye
>15 rem
>75 rem
Skin,
extremities,
organ
>50 rem
>250 rad
Summarized from 25 TAC 289.202 (xx)
Summary of Reported Incidents in Texas from 1988-1997
Unauthorized
Disposal
Transportation 3%
Unauthorized Unauthorized Release
Possession
0%
0%
Uranium Spill
1%
Accident
2%
Source Lost
7%
Source Found
4%
Source Fire
1%
Source Downhole
2%
Unauthorized Source
Use
Unauthorized Storage
0%
0%
Source Stolen
3%
Badge Overexposure
14%
Contamination
4%
Elevated Bioassay
1%
Equipment Damaged
2%
Improper Storage
0%
Source Disconnect
3%
Improper Transport
0%
Irregularity
8%
Leaking Source
3%
Safety Violations
0%
Radiation Injury
1%
Malfunction
3%
(n=2,026)
Overexposure
28%
Misadministration
8%
Reported Incidents in Texas
1988-1997 (n = 2,126)
Figure 2: Summary of overexposure and total incidents reported to the Texas
Department of Health, Bureau of Radiation Control from 1988 to 1997.
300
279
264
256
Number of Events
250
200
267
1994 - Revision of
regulations
(10CFR20).
206
201
190
168
164
150
Total Incidents
131
100
101
100
73
78
83
50
78
39
16
0
1986
1988
1990
1992
Year
1994
10
1996
Overexposure
15
1998
Results by Total Dose
>100 rem Not Reported
0% Other
5%
25-100 rem
1%
5%
10-25 rem
6%
5-10 rem
14%
1.25-5 rem
69%
Medical Decisions Based on Dose
(whole body dose, not considering localized doses, such as to hands or feet)
Consensus Summary on the Treatment of Radiation Injuries
Triage and Standard Emergency Care
Mild
<200 Rad
Moderate
200-500 Rad
Severe
500-1,000 Rad
Lethal
>1,000 Rad
Close observation
Daily CBC/platelets
Reverse isolation
Intensive care
Gut decontamination
Growth factors
Reverse Isolation
Intensive care
Gut decontamination
Growth Factors
Symptomatic
Suppotive care
Growth factors
Marrow/peripheral blood transplantation
Marrow/peripheral blood transplantation
Advances in the Biosciences, Vol.94 pp. 325-346, 1994 Elsevier Sciences Ltd. Great
Britain
Information Needed
In the absence of personal dosimetry or
portable survey instrument measurements,
the following is needed to develop some
estimate of the dose:
„
„
„
„
„
Isotope (or source)
Activity (or strength)
Exposure configuration (hand, pocket, distance,
inhalation?)
Duration
Source containments (sealed or unsealed)
Key point – how accurate do you need to be?
Four Overexposure
Configurations
Gamma external to whole body
Neutron source external to whole body
Beta skin dose
Inhalation
Gamma Sources
Common sources
„
„
„
„
Cs-137
Co-60
Ir-192
(note –these sources accounted for 60% of
all the overexposures examined in Texas,
and are likely contaminants for “dirty
bombs”)
Worker holds 100-Ci Cs-137
source for 15-min
By thumb rule 6CEN/d2:
6 × 100 × 0.6616 × 0.85 /(1 ft ) 2 = 774rad(± 20% )
By Specific Exposure Rate Constant (Γ):
2
R
m
0.33
h Ci
×100Ci
(0.1m )
2
× 0.955rad
R
× 0.25h
= 788rad
„
„
This assumes that the source was held 0.1m (approx. 4in) from body. You
would use the same formulation as above for the “on contact” reading of
the hand, but assume something like 1mm, 1cm, or 0.5in for the distance.
Discussion item: what health effects might you expect, and over what time
period, for such a dose scenario?
Neutron Sources
Common isotopic sources
„
„
„
PuBe
AmBe
PoBe
Worker places 5-Ci AmBe source in
chest pocket for 60 min
RHH Rule-of-Thumb (IAEA 1979) states that the
neutron fluence rate divided by 7000 gives an
approximation for the dose equivalent rate:
⎛ n ⎞
φ⎜ 2 ⎟
cm s ⎠
H rem ≈ ⎝
h
7000
(
)
A 5-Ci AmBe source emits approx. 1.3E6 neutrons
per cm2 per s at 1cm (assumed for on-contact):
H = 1.3E 6 n
2
cm s
÷ 7000 ≈ 186 rem
h
Worker places 5-Ci AmBe source in
chest pocket for 60 min (con’t)
Another, more involved method includes a “first collision
approximation:”
•
n
in
(
D = ∑ φ (En )× En × ∑ N iσ i (En )
1
„
i1
f
i
)
⎛⎜ Gy ⎞⎟
⎝ s⎠
This approximation overestimates the dose of the first collision by
forcing each (elastic) collision to result in the transfer of one-half
the neutron kinetic energy. This overestimation is then offset
because each neutron only undergoes one collision.
Worker places 5-Ci AmBe source in
chest pocket for 60 min (con’t)
With a 5-Ci AmBe source, at a distance of 1-cm, in contact for
one hour, for a reference energy spectrum (Gollnick), this
method gives, for the 0.26-MeV energy bin example:
E (MeV) E (J)
Element
M
1.56E+05
0.26 4.2E-14 O
C
H
N
Na
Cl
% Mass
71.39
14.89
10
3.47
0.15
0.1
N (atoms/k f
2.69E+25
6.41E+24
5.98E+25
1.49E+24
3.93E+22
1.70E+22
0.111
0.142
0.5
0.124
0.08
0.053
Dose Rate (tissue, rad/run (hour Total Dose (Rads)
1.75E-04
1 6.29E-01
„
Œ(barns) NŒf
3.63 1.08E+01
3.75 3.41E+00
8.5 2.54E+02
3.25 6.00E-01
3.128 9.83E-03
1.701 1.53E-03
Sum
2.69E+02
Discussion: why is neutron dose estimation so difficult? Hint: How
do scattering and absorption cross-sections change with neutron
kinetic energy?
Worker places 5-Ci AmBe source in
chest pocket for 60 min (con’t)
Summing over all energy bins in
the assumed AmBe distribution:
Approx. 183 rad in 1 hour
„
Discussion: What would you do
if there were an appreciable
thermal component to the
AmBe source spectrum?
E
0.1
0.13
0.17
0.2
0.26
0.34
0.42
0.5
0.65
0.825
1
1.33
1.67
2
2.6
3.4
4.2
5
6.5
8.25
10
13.3
Fractional E Dose rate (rad/s)
0.005 4.06E-05
0.007 6.95E-05
0.007 8.15E-05
0.01 1.28E-04
0.012 1.75E-04
0.013 2.20E-04
0.015 3.13E-04
0.017 3.53E-04
0.018 4.18E-04
0.02 5.32E-04
0.023 7.40E-04
0.027 9.53E-04
0.03 1.08E-03
0.042 1.64E-03
0.058 2.50E-03
0.098 5.19E-03
0.135 7.47E-03
0.158 9.16E-03
0.145 8.36E-03
0.135 8.37E-03
0.04 2.57E-03
0.005 3.52E-04
Total Dose Rate (rad/s)
Total in rad/hr
5.07E-02
1.83E+02
Beta Sources
Common sources
„
„
„
„
„
H-3
C-14
P-32
S-35
Ca-45
Lab tech spills 250μCi of P-32
on skin
Rule of thumb: for beta particles energies
>0.6-MeV, dose rate through the skin is
9rad/h per 1μCi/cm2:
⎛ rad
⎞
⎜
⎟ 250 μCi
9⎜ h
× 0.5h = 112.5rad
⎟×
2
μ
Ci
10cm
⎜
⎟
cm 2 ⎠
⎝
„
This assumes 0.5h elapses until worker is
completely decontaminated and that the
contaminated area amounted to 10 cm2.
Lab tech spills 250μCi of P-32
on skin (con’t)
Beta particles are observed to decrease
exponentially (approximate) in
traversing matter, in spite of their being
directly ionizing radiation, because:
„
„
All electrons follow a tortuous path in
matter due to their small mass, and
Betas are “born” over a spectrum of kinetic
energies.
Lab tech spills 250μCi of P-32
on skin (con’t)
This fact enables us to make use of an
empirical approximation for a beta
interaction coefficient*:
μ β ,air = 16(Tmax − 0.036)
−1.4
μ β ,tissue = 18.6(Tmax − 0.036)
⎛⎜ cm 2 ⎞⎟
g⎠
⎝
−1.37
*Cember 1996
⎛⎜ cm 2 ⎞⎟
g⎠
⎝
Lab tech spills 250μCi of P-32
on skin (con’t)
This “beta-ray absorption coefficient” may be
used to determine on-contact skin dose:
•
D β ⎛⎜ Gy ⎞⎟ = ⎛⎜ Bq 2 × tps × 0.5 × Tavg MeV ×1.6 E − 13 J
Bq
t
MeV
⎝ h ⎠ ⎝ cm
2
⎛
⎞⎟ × 3.6 E 3 s × e − μ β ,tiss ×0.007 ⎞ ÷
cm
× μ β ,tiss ⎜
⎟
g⎠
h
⎝
⎠
„
0.001
J
g
Gy
This assumes half of the beta particles are
directed into the skin, the remainder into
surrounding air. This also assumes that a depth
of 0.007g/cm2 is the critical depth for the basal
layer of skin.
Lab tech spills 250μCi of P-32
on skin (con’t)
Evaluating for P-32 (Tmax=1.71-MeV, Tavg=0.7-MeV),
at 250μCi over 10cm2 spill area:
μ β ,tissue = 18.6(1.71 − 0.036)
−1.37
⎛⎜ cm 2 ⎞⎟ = 9.18
g⎠
⎝
•
D β ⎛⎜ Gy ⎞⎟ = ⎛⎜ 9.25 E 5Bq 2 × tps × 0.5 × 0.7 MeV ×1.6 E − 13 J
Bq
t
MeV
cm
⎝ h⎠ ⎝
2
× 9.18⎛⎜ cm ⎞⎟ × 3.6 E 3 s × e −9.18×0.007 ⎞⎟ ÷
g⎠
h
⎝
⎠
0.001
J
g
Gy
= 1.605 Gy
h
Lab tech spills 250μCi of P-32
on skin (con’t)
„
If we integrate this dose rate over the time that
any activity remains on the person we have a
conservative estimate of the skin dose. For
example, using our previously calculated skin dose
rate and assuming that contamination is
completely removed within one-half hour of the
occurrence:
•
1.605⎛⎜ Gy ⎞⎟
h⎠
Do
⎝
− λt
− 2.02 E −3×0.5
DT =
1− e =
1
−
e
2.02 E − 3 h −1
λ
(
)
(
( )
= 0.802Gy ( skin) ≅ 80rad
)
Lab tech spills 250μCi of P-32
on skin (con’t)
If we use the previous formula normalized to an areal activity of
1 Bq cm-2, we can calculate a dose conversion factor (DCF) for
any beta emitting nuclide, which may then be used at any time
in the future (like a Γ, but for beta skin contamination):
⎞
⎛ Gy
⎟ ⎡ tps
⎜
= ⎢⎛⎜
× 0.5 × Tavg MeV ×1.6 E − 13 J
DCF ⎜ h
⎟
Bq ⎟ ⎣⎝ Bq
t
MeV
⎜
cm 2 ⎠
⎝
J
⎤
0.001
⎥
2
− μ β ,tiss ×0.007 ⎞
g
⎛
⎞
cm
s
× μ β ,tiss ⎜
× 3.6 E 3 × e
⎥
⎟÷
g ⎟⎠
h
Gy
⎝
⎠
⎥
⎥⎦
„
Discussion: Can we say that μ β,tiss is similar to the μ/ρ we use for
photons? μtr/ρ? μen/ρ?
Lab tech spills 250μCi of P-32
on skin (con’t)
Another method makes use of a set of tabular conversion
factors derived from a complex computational transport model:
⎛ Sv
⎞
⎛ rem
⎞
⎜
⎟
⎜
⎟
y
rem
y
Bq
⎛
⎞
⎟ × 422⎜
= 8.862⎜ h
2.1E − 2⎜
⎟
⎟
Bq ⎟
Sv h μCi ⎠
Ci
μ
⎝
⎜
⎜
⎟
2 ⎟
2
⎜
cm ⎠
cm ⎠
⎝
⎝
⎛ rem
⎞
⎜
⎟
250 μCi
rem or 111rem in 0.5h
h
×
≅
8
.
862
221
.
55
⎜
⎟
μCi ⎟
h
10cm 2
⎜
cm 2 ⎠
⎝
*RHH and Gollnick, after Kocher and Eckerman 1987.
Discussion: what might be the reason for the difference in
results between these two methods?
Worker Inhales 30mCi I-125
Divide given activity by the stochastic ALI (for WB
risk) or non-stochastic ALI (for organ risk):
30,000 μCi
30,000 μCi
„
„
„
200 μCi
60 μCi
× 5rem = 750rem(WB − CEDE )
× 50rem = 25,000rem(thyroid CDE )
The ALI(NS) is appropriate for the thyroid, rather than the ALI(S), and this
is indicated in 289TAC25. These ALIs incorporate intake-to-uptake models,
pharmacokinetic models for distribution, all source-target geometries for
said models, and all radiative emissions.
Approx. 30% of the iodine uptake is incorporated by the thyroid with a 40d
biological half-life. The remainder circulates throughout the body and is
eliminated with a 10d half-life.
Discussion: We often use the term “seeker” (e.g., bone seeker, thyroid
seeker) to describe a radioactive chemical species – is this bad or good?
Who Do I Call For Assistance?
California Radiologic Health Branch
„
916-327-5106
REAC/TS
„
423-576-3131
Radiation Internal Dose Information Center
„
423-576-3449
Key reference:
„
Ricks, RC, Berger, ME, O’Hara, F; The Medical
Basis for Radiation-Accident Preparedness,
Parthenon Publishing Group, New York, 2002
Current Developments: “Domestic
Radiological Terrorism”
Foreseeable terrorist threats involving sources of
radiation, in rank order of probability
„ 1. Dirty weapon
Š conventional explosive dispersing radioactive
sources
„ 2. Conventional explosive at “nuclear facility”
Š a dispersal event rather than a criticality, or
nuclear fission event
„ 3. Tactical nuclear device
Š device capable of criticality, or fission
Š self-built or stolen
Why are “Dirty Bombs”
Ranked First?
Conventional explosives can be obtained from
many sources
Although not as readily available, potential
radioactive contamination sources could take
several forms:
„
„
Examples: gauges, testing sources, waste
materials
(note: sources not necessarily domestic)
High “population terror” potential, given
public’s apprehension about radiation
Of 26 terror acts in US in past 22 years, 17
have involved explosives (www.cdi.org)
Why Aren’t Nuclear Facilities
Ranked First?
Commercial nuclear facilities are guarded 24
hrs/day, 365 days/yr by heavily armed, well
trained personnel
Security systems well coordinated with local,
state and federal agencies
Plants occupy sites with buffer zones
Containment structures quite robust: 4-6 ft
concrete, reactor vessels 9-12 inches thick
Other safety design features
What About Tactical Nuclear
Weapons?
Although small “backpack” devices have been
developed, expected use unlikely given
difficulties with obtaining, maintaining, and
operating such devices
Nonetheless, in current climate, possibility of
use exists, hence some discussion of effects
and countermeasures is warranted
Detonation may not be limited to ground or
underground bursts – elevated detonation in
highrise building plausible
Conventional Terrorist Explosion:
Is It “Dirty”?
Emergency responders should always
perform monitoring at site for various types
of radiation emissions
If radiation detected, establish appropriate
exclusion zones, handle casualties accordingly
Smoke may contain radioactive materials, so
respiratory protection necessary
Secure area
Notifications for added assistance and
controls
Population doses likely very low
Explosion at a Nuclear Facility
Examples include a nuclear power facility,
radioactive waste site, or nuclear weapons
facility
„
„
„
„
„
Emergency responders would be prepared and
expect to perform monitoring at site
Many existing monitoring capabilities
If release detected, plans enacted, exclusion
zones established, notifications made, casualties
handled accordingly
Monitoring for offsite releases and meteorological
conditions
Population doses projected to be low given
existing controls in place
Nuclear Weapon Detonation
Assumed to be a single, low yield device (20 kT)
„
„
„
„
„
„
Blast – overpressurization, accelerated debris
Heat – intense fireball, ignite materials far from
center
Initial radiation – prompt emission of high radiation
levels (EMP)
Residual radiation – activation products and
contamination, fallout dependant on environmental
conditions
Crater formation – large amounts of ground
displacement
Ground shock – disrupt utilities, damage structures
Explosion of a Nuclear Weapon
Assume a 20 kT ground burst
„
„
„
„
„
„
180 ft radius crater
Within ½ mile, 50% population fatalities from debris
impact
Within 1.8 mile radius, 50% population fatalities from
thermal burns
Within 1 mile radius, 50% population fatalities from
immediate radiation exposures
Within 7.7 mile radius, 50% population fatalities from
rad exposures in first hour
For purposes of comparison, 40 acres is approximately
a circle with a radius of approximately 750 ft
Emergency Medical Response
A significant challenge (Hiroshima 20 kT airburst)
„
„
„
„
45,000 deaths first day, 91,000 injured.
of 45 hospitals, only 3 left standing
of 298 physicians, only 28 uninjured
of 1780 nurses, 1654 were casualties
On-scene triage: wounds, burns, exposure,
contamination
Radiological assessment of patients with and
without immediately observable injuries
Decontamination
Pharmacological protection for fallout?
Total overexposures in Texas, 1970 to 2002
300
250
Total overexposures
200
Total overexposures
150
100
50
0
1970
1975
1980
1985
1990
Year
1995
2000
2005
Rig count 1970 to 2004 and Total overexposures 1970 to 2002, in Texas
300
1400
1200
250
Rig count
1000
Total overexposures
Rig count
800
150
600
100
400
50
200
0
1970
1975
1980
1985
1990
Year
1995
2000
0
2005
Total overexposures
200
Summary
Radiation overexposures are relatively rare events, but do
happen
Medical intervention decisions are based on dose estimations
To estimate dose, basic information is needed
The initial estimation need not be extremely accurate
Remember to always check for contamination – both inside and
out
Given possibility of domestic terrorism, now is the time to begin
reviewing response capabilities and procedures –especially the
worried well issue
Keep a watch on rig count – at least in Texas, overexposures
are linked to this metric
Help is out there – so keep the contact information readily
accessible
Web References/Resources
Center for Defense Information available at www.cdi.org/terrorism
Office of Technology Assessment: The Effects of Nuclear War, May
1979, available at www.wws.princeton.edu/cgibin/byteser.prl/~ota/disk3/1979/7906/790604.PDF
Armed Forces Radiobiology Research Institute, available at
www.afrri.usuhs.mil
Texas Division of Emergency Management at
www.txdps.state.tx.us/dem/
Texas Department of Health Bureau of Radiation Control at
www.tdh.state.tx.us/ech/rad
Health Physics Society at www.hps.org
South Texas Chapter of the Health Physics Society at www.stchps.org
Texas Public Health Training Center at www.txphtrainingcenter.org
Text References/Resources
NCRP Report No. 138 Management of Terrorist Events
Involving Radioactive Materials, October 2001. available at
www.ncrp.com
Glasstone, S., Dolan, P.J. The Effects of Nuclear Weapons,
Third Edition. U.S. Dept of Defense and US Dept of
Energy, 1977, US Government Printing Office,
Washington, DC, available at www.gpo.gov.
Landesman, L.Y. Public Health Management of Disasters,
The Practice Guide. American Public Health Assoc. 2001,
Washington, DC, available at www.apha.org
Schull, WJ Effects of Atomic Radiation: A Half Century of
Studies from Hiroshima and Nagasaki, Wiley-Liss, 1995.